Gyratory compaction apparatus for creating compression and shear forces in a sample material

ABSTRACT

The present invention contemplates a gyratory compaction apparatus for creating compression and shear forces in a sample material, the apparatus using a single roller to accomplish the gyration comprising a hollow cylinder mold including first and second end plates in slidable engagement with the mold at respective first and second open ends, with a chamber inside the mold for receiving the sample material, a support frame having an interior suitable for receiving the mold therein, a compression mechanism for compressing the sample material, and a gyratory assembly comprising a rotational drive motor having a drive shaft aligned along the longitudinal axis of the support frame interior, a cam mounted at the end of the drive shaft, a gyratory plate having an inner housing for encompassing and operably engaging the cam including a spring biased plunger operably engaging the cam and a first outer angular contact bearing for operably engaging the mold inner surface and a driven plate operably mounted to the support frame with a second angular contact bearing and operably coupled to the gyratory plate with a pin mounted eccentric to the longitudinal axis of the cylindrical interior and an annular planar thrust bearing concentric to the pin so that when the cam is driven in a first direction the gyratory plate is rotated concentrically about the longitudinal axis of the cylindrical interior and when the cam driven in an opposite second direction, the cam engages the plunger pivoting the gyratory plate about the axis of the pin radially displacing the gyratory plate and first angular contact bearing so that the gyratory plate rotates eccentric to the longitudinal axis while the first angular contact bearing tilts the mold to a specified angle relative to the longitudinal axis of the housing and gyrates the mold about the specified angle while the sample material is compressed within the mold.

FIELD OF THE INVENTION

This invention relates generally to devices for testing materials, morespecifically to a device for accomplishing compaction while gyrating thespecimen container and in a specific instance relates to a portablegyratory compactor for the testing of specimens of asphalt pavingmaterials.

BACKGROUND OF THE INVENTION

In the general field of materials testing, a number of different typesof material mixtures are amenable to testing by subjecting specimens ofthe material to compressive forces while concomitantly imposing shearforces on the mixture and then measuring the degree of compaction thespecimen undergoes in response to the compression and shearing. As anexample, such testing has been found to be useful in measuring asphaltmixture samples in the evaluation of the asphalt mixture used in pavingroad surfaces as a measure of the quality of the road surface.

An asphalt paving mixture generally comprises a crushed rock aggregate,a bituminous binder, and air voids. Because the individual particles ofrock constituting the aggregate are irregular in shape and size, wheninitially mixed, there are numerous small air voids in the mixture. Thestrength, durability and cost of asphalt pavement are directly relatedto the type and size of the particles of rock found in the aggregate,the proportion of binder in the aggregate and the amount of air voids inthe final pavement after it has been rolled out, along with otherfactors. Too much bituminous binder, for instance, under compressionfills in substantially all of the air voids and causes flowing of theasphalt mixture in response to the compressive forces which eventuallyleads to early deterioration of the road surface. Too little bituminousbinder can leave the road surface brittle and porous, subjecting thesurface to cracking and susceptible to freeze-thaw disruption with theentry of water for roads situated in those climates subjected tofreezing temperatures.

The purpose of gyratory compaction testing is to subject a sample of theasphalt mixture to compression and shear forces to determine the degreeof compaction achievable which is directly related to the amount ofbituminous binder and air voids present in the asphalt mixture. Knowntest parameters are the density of the aggregate, bituminous binder, andweight of the sample. The degree of compaction is then used to calculatethe change in density due to compaction of the sample during the testrun. The results are then useful to determine whether a particularasphalt paving mixture will have the strength and durability requiredfor the anticipated traffic conditions on a particular roadway beforethe asphalt is applied to the roadway.

The United States Department of Transportation Federal HighwayAdministration Publication No. FHWA-SA-95-003, Background of SuperpaveAsphalt Mixture Design and Analysis (February 1995) describes a gyratorycompaction test for asphalt paving material and the conclusions whichmay be inferred from gyratory compaction testing. Devices for performingthese tests have been developed by Troxler Electronic Laboratories,Inc., Pine Instrument Company and others.

These guidelines call for precise, reproducible compressive forces,angles of gyration and specified temperatures for testing a samplewithin the mold. It is a combination of the compressive force and angleof gyration that determines the resultant shear force placed on thespecimen. Precise control of compression and angle of gyration iscritical in obtaining accurate test results that are reliable inpredicting the actual conditions of density, alignment of aggregate andappropriate elastic properties within the asphalt mixture. The propertemperature is also critical in maintaining the appropriate viscosity ofthe sample during the test so as to approach similar to actualconditions during the paving procedure.

In general, the testing protocol requires that a heated and pre-weighedspecimen of the asphalt paving mixture be placed in a cylindrical mold.The specimen is then compressed to a predetermined pressure and aninitial density calculation is determined. Since the density of the rockand bituminous binder are known, the measured density, in conjunctionwith the known values of two of the components, is used to calculate thepercentage of air voids in the sample. The specimen mold is then movedin a gyratory fashion at a small angle relative to, and around, the longaxis of the compressive force as applied to the sample through mold endplates while the sample is kept under a specified amount of compression.The compression force and the gyratory motion of the mold combine toproduce a shear stress in the specimen as long as at least one of theend plates remains perpendicular to the longitudinal axis of thecompressive force. This gyratory compaction testing is designed toreproduce the shear stresses induced in the asphalt mixture when it islaid down and undergoes vibratory compression from the paving rollers.As noted above, it is the resulting compacted paved asphalt that willdetermine the quality of the road surface.

This shear stress causes individual particles of rock to move, realignand perhaps even to break, thus filling a substantial amount of thevoids and reducing the volume of the paving mixture in the mold. Thestrength, durability, elasticity and thus the suitability of the pavingmixture for anticipated traffic conditions is inferred from thereduction in volume, and therefore, change in density of the specimenand other observations made during the test.

The principles of gyratory compaction testing are more fully explainedin the above-referenced publication. However, if the gyratory compactiontest is to be precise and reliable, the compression force and the angleat which the mold cylinder is inclined as it is gyrated must be heldconstant within a very narrow range. Generally, maintaining the angle ofinclination precisely within the narrow range specified by the testingprotocol is far more difficult than maintaining the compressive forcewithin the specified range.

U.S. Pat. No. 2,972,249 issued to McRae, et al., discloses a gyratorycompactor device that holds the specimen within a mold chuck between twoopposed compression rams. Shear forces are generated by gyrating themold chuck around the long axis of the compression rams. The mold isgyrated using multiple rollers mounted in a chuck mold oscillator frame,the wheels being offset in relation to each other and engaging a flangeon the outside of the chuck mold.

U.S. Pat. No. 5,456,118 issued to Hines, et al., also discloses agyratory compactor that accomplishes gyration by tilting the mold. Thisdisclosure uses an external mold carriage assembly attached to arotatable circular base below and a carriage tilt link assembly above.Just as with the McRae device, multiple rollers engage an outside flangerim of the mold and spin around the outside of the mold in a planetilted to the axis of the compression ram. A secondary consequence ofthis device is the lateral moment arm of force exerted on thecompression ram as the mold and contents are gyrated. Any deflection inthe shaft of the compression ram shaft towards the induced tilt axisdecreases the amount of shear forces on the sample and changes thetesting environment. The amount of lateral moment arm force on thecompression ram shaft is not reproducible from test to test. The Hinesdevice also requires the removal of the mold from the tilting assemblyto facilitate loading and extracting the test sample. This severelycurtails the number of samples that can be run over time because thedevice requires realignment and recalibration for each run and the moldmust be brought back to testing temperature before the next test run.

U.S. Pat. Nos. 4,942,768 and 5,036,709 issued to McRae disclose agyratory compactor that tests a specimen held in a mold by a chuck. Thechuck, not the mold, is then gyrated using a spinning offset rollerassembly engaging a flange to the outside of the chuck as the specimenis compressed from the bottom while held in a stationary mold. Gyrationof the chuck and its end plate in contact with the specimen effects akneading action on the specimen within the mold. As with the prior twodevices mentioned above, this device uses a bulky assembly, withmultiple rollers, spinning to the outside of the specimen mold toaccomplish the gyration.

These gyrating assemblies have resulted in testing machines that arelarge, heavy and therefore not transportable. Their expensesubstantially influences, and limits, the number of machines available,increasing the likelihood that large mixtures of asphalt will be pavedout having never been tested for appropriateness of use. These gyratoryinducing mechanisms, using multiple rollers outside the mold against oneor more flanges also to the outside, require many moving parts held in alarge framework and cabinet.

At the conclusion of the gyratory compaction test, the specimen must bestripped from the mold. The Hines and earlier McRae machines discussedabove require that the mold be removed from the machine and insertedonto another device where the specimen is pressed out of the mold. Thesemachines must be precisely readjusted every time a sample is run tomaintain the angle of inclination because the entire setup has to betaken down and reassembled between test runs. Additional time is lostbringing the mold back up to temperature before the next sample can berun in that mold. While they are suitable for laboratory use, thosemachines are not readily adaptable for mobile operation and testingsamples of paving mix at the point of mixing or at the job site.

Consequently, there is a need for a simple, lightweight gyratorycompaction testing machine which controls compression forces andmaintains the angle of inclination precisely with minimal adjustment andwhich may be readily mounted on a van, truck or other vehicle andoperated at the site where the asphalt is mixed and/or the roadway isbeing paved. There is a need for a gyratory testing machine which canstrip the specimen from the mold without removing the mold from thegyratory compaction testing machine.

SUMMARY OF THE INVENTION

Material testing is a broad area and encompasses a number of types oftests which include shearing and compaction. The above referenced UnitedStates Department of Transportation Federal Highway Administration testis a specific example of a testing protocol to be used on asphalt thatis to be laid and rolled in forming a road surface. In brief, the testrequires an approximately eight pound sample of the asphalt, held at300° F., to undergo compaction at 600 Kpa and shear stress generated bya gyratory tilting at an angle of 1.25°±0.025. Additionally the samplemust be held between two end plates that remain parallel to each otherduring the testing. In order to accumulate test data that is meaningfulunder conditions that are reproducible, a gyratory compactor mustconform to high standards of precision and reliability.

The present invention contemplates a gyratory compaction apparatus forcreating compression and shear forces in a sample material, theapparatus using a single roller acting within a cylinder mold toaccomplish the gyration. The apparatus comprises a hollow cylinder moldopen at both ends and includes a first and second end plates in slidableengagement within the mold at respective first and second open ends.These plates in conjunction with the mold creates a chamber between theend plates for receiving the sample material. A support frame isprovided that defines a hollow cylindrical interior suitable forreceiving the mold therein. A compression mechanism, mountable on thesupport frame, is used to compress the sample material. The compressionmechanism includes a rod aligned along a longitudinal axis of thecylindrical interior and operably engages the first end plate. Agyratory assembly, removably mountable between the support frame andmold and engageable with the second end plate comprises a rotationaldrive motor for reversibly rotating the gyratory assembly which has adrive shaft proximate the second open end and aligned along thelongitudinal axis of the cylindrical interior. There is a cam mounted atthe end of the drive shaft along with a gyratory plate having an innerhousing for encompassing and operably engaging the cam which includes aspring biased plunger operably engaging the cam. A first angular contactbearing is mounted to the cam plate for rollably engaging a mold innersurface proximate the second open end. A driven plate is operablyengageable with the support frame through a second angular contactbearing and operably coupled to the gyratory plate with a pin mountedeccentric to the longitudinal axis of the cylindrical interior. There isan annular planar thrust bearing between the gyratory plate and drivenplate concentric to the pin so that when the cam is driven in a firstdirection the gyratory plate is rotated concentrically about thelongitudinal axis of the cylindrical interior and when the cam is drivenin an opposite second direction, the cam engages the plunger pivotingthe gyratory plate about the axis of the pin so that the gyratory platerotates radially relative to the longitudinal axis and now rotateseccentrically around the longitudinal axis. The first angular contactbearing thus tilts the mold to a specified angle relative to thelongitudinal axis of the cylindrical interior and gyrates the mold aboutthe specified angle while the sample material is compressed within themold.

A preferred embodiment of the present invention for a gyratory compactorapparatus for subjecting a material sample to controlled shear andcompaction forces comprises a hollow cylindrical housing having an innercylindrical wall, a bottom and a removable top. There is a first anglerim mounted on the bottom surface within the cylinder concentric to theinner cylindrical wall and having a frusto-conical outer surface. Asecond angle ring is adjustably mounted to the inner cylindrical wallhaving a frusto-conical inner surface and is concentric to the innercylindrical wall, the inner surface is substantially parallel to thefirst angle rim outer surface and has an overall inner diameter greaterthan an overall outer diameter of the first angle rim. A hollow moldcylinder open at both ends for placement within the housing, has aninner and an outer mold surface and rounded first and second ends. Thefirst rounded end is suitable for resting on the angled outer surface ofthe first angle rim. The mold cylinder is tiltable on the first anglerim and provides for the second rounded end to engage the angled innersurface of the second angle ring. The mold is completed using aremovable first end plate and a removable second end plate, both endplates in slidable engagement with the mold inner surface, the innermold surface and both end plates defining a volume suitable forreceiving the material sample. A motor is mounted to the top andincludes a drive shaft projecting into the housing through a hole in thetop centered along the longitudinal axis of the housing. A compressioncylinder and rod are mounted to the housing bottom with the rodprojecting into the housing through a hole in the bottom centered alongthe longitudinal axis of the housing, the rod operably engaging thefirst end plate. A controller subsystem is operably connected to themotor and compression cylinder for controlling the motor and compressioncylinder. A gyratory assembly, operably attached on an inner surface ofthe top, comprises a cam, a cam plate, a gyratory plate, a first angularcontact bearing, and a second angular contact bearing. The cam ismounted at the end of the drive shaft. The gyratory plate has an innerhousing for encompassing and operably engaging the cam and includes aspring biased plunger operably also engaging the cam. The first outerangle contact bearing for operably engaging the mold inner surface fitsover the cam plate. The driven plate is operably mounted to the top withthe second angular contact bearing and operably coupled to the gyratoryplate with a pin mounted eccentric to the long axis of the housing.There is included an annular thrust bearing concentric to the pin sothat when the cam is driven in a first direction the gyratory plate isturned concentrically about the longitudinal axis of the housing andwhen the cam is driven in an opposite second direction, the cam engagesthe plunger pivoting the gyratory plate about the axis of the pin sothat the gyratory plate moves radially from the longitudinal axis of thehousing and spins eccentrically around the longitudinal axis. The firstangular contact bearing, riding on the cam plate, also moves radiallywith the gyratory plate and tilts the mold to operably engage the secondangle ring at a specified angle to the longitudinal axis of the housingand gyrate the mold about the specified angle while the sample materialis compressed within the mold.

A general object of this invention is to provide an apparatus whichholds a cylindrical mold at a precise angle of inclination while themold is gyrated. Accordingly, the invention constrains the mold betweentwo parallel structures as the mold is gyrated. Thus the cylindricalmold maintains a precise angle of inclination even though the mold maybe displaced along its longitudinal axis as the mold is gyrated.

An additional object of the invention is to provide a simple mechanicalmeans to align the parallel structures and thus insure that theapparatus can accommodate cylindrical molds which vary slightly inlength, outer diameter, eccentricity and other physical characteristicsand still maintain the precise angle of inclination required by thegyratory compaction testing procedure.

A further object of the invention is provide a gyratory compactiontesting apparatus in which the gyratory motion of a cylindrical mold isproduced by forces acting on the inner surface of the mold, and moreparticularly by the eccentric rotary motion of a component of theapparatus which engages the inner surface of the mold and forces themold cylinder into positive contact with the parallel structures whichhold the mold in alignment at the desired angle of inclination as themold cylinder is gyrated.

An additional further object of the invention is to provide acombination of bearings which enable the rotating components of theapparatus simultaneously to withstand compressive forces directed alonga central axis of rotation, rotate freely about the central axis ofrotation, and permit one of the rotating components to move radially,away from the central axis of rotation, thus rotating in an eccentricmanner about the central axis of rotation to gyrate the mold.

Another object of the invention is to provide a means for extracting thespecimen from the cylindrical mold at the conclusion of the gyratorycompaction test procedure without removing the mold from the apparatus.

Another further object of the invention is to provide a gyratorycompaction testing apparatus which is safe, simple, light in weight,rugged and readily adaptable to mobile operation.

Other objects of the present invention and many of the attendantadvantages of the present invention will be readily appreciated as thesame become better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of the present invention;

FIG. 2 is a side elevational view and cross section of the upper portionof the embodiment depicted in FIG. 1 with the cross section taken alongline 2--2 of FIG. 1;

FIG. 3 is a side elevational view of the lower portion of the embodimentdepicted in FIG. 1;

FIG. 4 is an exploded perspective view of a gyratory assembly componentof the embodiment of the present invention depicted in FIG. 1;

FIG. 5 is a bottom plan view of a gyratory cam component depicted inFIG. 4;

FIG. 6 is a bottom plan view of a cam plate component depicted in FIG.4, with details of its upper surface and pins of a driven plate shown inphantom;

FIG. 7 is a bottom plan view of the depiction shown in FIG. 6 afterhaving spun the gyratory cam to pivot the gyratory plate to its gyratoryposition relative to the pins of the driven plate; and

FIG. 8 is a schematic diagram of a gyratory compaction control circuituseful to the embodiment depicted in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In reference to FIGS. 1 through 4, wherein like numbers refer to likecomponents throughout the Figures, there is disclosed a gyratorycompactor apparatus 10 comprising a cylinder housing 12, a mold cylinder14, a first angle rim 16, a second angle adjustment rim 18, a hydrauliccylinder 20, a motor 22, a gyratory compaction control module 24, and agyratory assembly 26.

Cylinder housing 12 further includes a housing wall 30, a lid or top 32,and a base plate or bottom 34. Top 32 includes a hole 33 concentric tothe longitudinal axis of housing wall 12. Bottom 34 includes a hole 58,also concentric to the longitudinal axis of housing wall 12.

Mold cylinder 14 includes a cylinder wall 36, a mold heater 37, a baseplate or first end plate 42, and a sample cap plate or second end plate44 which as a unit define a test sample volume (sample material S inFIG. 2). Additionally, cylinder wall 36 also includes a rounded firstend 38, a rounded second end 40 and an inner surface 35.

First angle rim 16 includes a outer frusto-conical or beveled surface 45suitable for rolling engagement of cylinder wall 36 at rounded first end38. First angle rim 16 facilitates aligning cylinder mold 14 to thelongitudinal axis of housing wall 30 and motion of rounded first end 38when cylinder mold 14 is gyrated. When cylinder wall 36 is placed withincylinder housing 12, an additionally secured positioning is achievedwhen cylinder wall 36 fits over a pair of position index pins 39.

Second angle adjustment rim 18 includes an inner frusto-conical orbeveled surface 46. Beveled surface 46 is substantially parallel tobeveled surface 45. As used in this sense, parallel should be understoodto mean that a plane passing through the centers of first angle ring 16and second angle adjustment ring 18 and both surfaces 45, 46 willintersect surfaces 45, 46 to produce substantially parallel lines.However, second angle adjustment rim 18 has a greater internal diameterthan the outer diameter of first angle rim 16. Beveled surface 46 issuitable for slidable contact engagement of rounded second end 40 ofcylinder wall 36 when cylinder wall 36 is tilted in the gyratory mode ofoperation described hereinbelow.

The distance between first angle rim 16 and second angle adjustment rim18 is adjustable by suspending second angle adjustment rim 18 in aplurality of adjustment blocks 48. This embodiment of the presentinvention anticipates the use of three adjustment blocks 48. Adjustmentblocks 48 are mounted to housing wall 30 using a screw 50 placed throughchannel spaces 52 and jam nuts 51 and threading adjustment screw 50 intoa mount 54. The plurality of adjustment blocks 48 may be raised orlowered on jam nuts 51 by threading screw 50 in and out of mount 54.Screw 50 has a fine thread to provide for minute changes in the heightof adjustment blocks 48 ensuring precise accuracy of tilt for cylindermold 14. This adjustment means permits the present invention to acceptcylinder molds which vary slightly in height, diameter, wall thickness,eccentricity and other characteristics and also compensates forvariations in the height, diameter, thickness, eccentricity and othercharacteristics of the angle rim and the angle adjustment rim as well asto compensate for other variances and tolerances in the construction andassembly of the apparatus.

Hydraulic cylinder 20 includes a cylinder rod 21 ending in a load cell56 that projects through a housing bottom hole 58 to reach and bemounted to a pressure plate 59 within cylinder housing 12. Hydrauliccylinder 20 and cylinder 21 are in line with the longitudinal axis ofcylinder housing 12 and housing wall 30. Compressive forces exerted byhydraulic cylinder 20 are exerted through cylinder rod 21 along thelongitudinal axis of housing wall 30. An anti-rotation rod 60 is mountedeccentric on pressure plate 59 and projects back through housing bottom34 so as to stabilize hydraulic cylinder 20 and cylinder rod 21 againstpossible rotational forces. Those skilled in the art will recognize thatmany hydraulic, pneumatic, mechanical, electrical and electromechanicaldevices are capable of generating the compression force required by thetesting procedure and thus are equivalent to the hydraulic cylinder androd illustrated in the drawings and may be employed in alternativeembodiments without departing from the scope and spirit of the presentinvention.

Motor 22 includes a motor mount adapter plate 62 for adapting a motor totop 32. Additionally, there is a motor gear assembly 66 operably drivinga drive shaft 64 extending through a hole 33 centered in top 32 so thatdrive shaft 64 is centered on and rotates around the longitudinal axisof housing wall 30.

Top 32 is openable and closable using a plurality of lid clamps 68threaded over a bolt 70 mounted to an outer side wall of housing wall 30so that lid clamp 68 may slide over and operably engage a lid clampbracket 72. The present invention anticipates the use of one or more andthe present embodiment uses three such lid clamps 68. When opened, top32 is supported by a lid lift 74 mounted over a lid lift spring 76 ofsufficient strength and biased to support the entire weight of top 32and motor 22, gyratory assembly 26 mounted thereto. Lid lift 74 may beswiveled to swing the entire top 32 away from the upper aspect ofhousing wall 30.

Gyratory assembly 26 includes a gyratory cam 80, a cam plate 90, agyratory plate 106, a first angular contact bearing 118, a driven plate124, and a second angular contact bearing 136. Gyratory cam 80 includesa plunger engaging surface 82, a non-gyratory drive surface 84, a driveshaft sleeve 86, and a gyratory drive surface 88. Drive shaft sleeve 86is keyed to mount over drive shaft 64.

Cam plate 90 includes a cam housing 92, an outer bearing shaft 94, agyratory driven surface 96 within cam housing 92, and a non-gyratorydriven surface 98 also within cam housing 92. Operably mounted withincam plate 90 is a plunger 100 having a plunger stem 102 operably coupledto a plurality of constant tension spring washers 104 biased to maintainplunger 100 against plunger engaging surface 82 of gyratory cam 80.

Gyratory plate 106 is fixedly mountable to cam plate 90 with a pluralityof mounting screws 108. Gyratory plate 106 includes a pivot pin hole110, a pin slot 112, a clearance hole 114, and a bearing groove 116.Clearance hole 114 provides a space in gyratory plate 106 through whichdrive shaft sleeve 86 may project.

First angular contact bearing 118 includes an inner bearing race 120 andan outer bearing race 122. Angular contact bearing 118 is mounted overbearing shaft 94 in a friction fit between the surface of bearing shaft94 and the surface of inner bearing race 120.

Driven plate 124 includes a pin plate 126, a bearing shaft 128, a driveshaft sleeve hole 130, a pivot or gyratory pin 132, and a slot pin 134.Pivot pin 132 and slot pin 134 are fixedly mounted in the under surfaceof pin plate 126 eccentrically but equal distantly placed from driveshaft sleeve hole 130 which is concentric about the longitudinal axis ofhousing wall 30. Pin plate 26 and gyratory plate 106 are operably matedthrough the interaction of a thrust bearing 150 which includes a rollerbearing 152 sandwiched between a first bearing race 154 and a secondbearing race 156. Thrust bearing 150 is centered about pivot pin 132 toaccommodate relative rotational motion of gyratory plate 106 relative topin plate 126. Each of these bearing races fit within respective bearinggrooves with second bearing race 156 nesting within bearing groove 116of gyratory plate 106. A comparable groove, not seen, in the surface ofpin plate 126 is suitable for nesting first bearing race 154.Additionally, pivot pin 132 aligns with pivot hole 110 and slot pin 134aligns with pin slot 112. Drive shaft sleeve hole 130 has an innerdiameter sufficient to accept drive shaft sleeve 86 in slidable butabuttable engagement.

Second angular contact bearing 136 includes an inner bearing race 138and an outer bearing race 140. Angular contact bearing 136 is placedover bearing shaft 128 and the assembly secured with a C-ring 146 placedwithin groove 148.

Gyratory compaction control module 24 includes a first mold angletransducer 160, a second mold angle transducer 166, a wire connection164 to angle transducer 160, a wire connection 170 to angle transducer166, a load cell wire connection 172, and a cylinder rod position wireconnection 174. Angle transducer 160 includes a plunger 162 springbiased so as to continuously rest the tip of plunger 162 against theouter surface of cylinder wall 36. Angle transducer 166 has a similarplunger 168 also spring biased to maintain constant contact between thetip of plunger 168 and the outer surface of cylinder wall 136. Angletransducers 160 and 166 are linearly spaced and in the presentembodiment are separated vertically along housing wall 30. Additionally,the present invention anticipates the use of a plurality of pairs ofangle transducers spaced sequentially about a cylinder housing 12. Thepresent embodiment utilizes two pairs mounted on opposite sides ofhousing wall 30 although any number of pairs are feasible.

The function of gyratory assembly 26 is to provide a single roller,i.e., first angular contact bearing 118, to operably engage inner wall35 proximate rounded second end 40 so that when gyratory assembly 26 isspun in a first direction, first angular contact bearing 118 isconcentric about the longitudinal axis of housing wall 30 and noshearing force is applied to sample material S. When gyratory assembly26 is spun in a second, opposite direction, first angular contactbearing is shifted radially in relation to the longitudinal axis ofhousing wall 30 by action of gyratory cam 80, tilting the longitudinalaxis of cylinder mold 14 in relation to the longitudinal axis of housingwall 30. As gyratory assembly 26 spins in this second direction, firstangular contact bearing 118 rolls against inner surface 35 gyrating theaxis of cylinder mold 14 about the longitudinal axis of housing wall 30.

The function of driven plate 124 is to counter any lateral moment forcesgenerated from the shearing and compressive forces from cam plate 90,gyratory plate 106 and first angular contact bearing 118 gyratingeccentric to the axis of driven plate 124 which is oriented to thelongitudinal axis of housing wall 30 and taking up compressive forcespassed through gyratory assembly 26 from hydraulic cylinder 20. Theseforces are countered by driven plate 124 in conjunction with secondangular contact bearing 136 in operable contact with top 32. The resultof this effort is to keep second end plate 44 perpendicular to thelongitudinal axis of housing wall 30 which maintains the accuracy andreproducibility of tests performed by gyratory compactor apparatus 10.Thrust bearing 150 provides a bearing surface between gyratory plate 106and driven plate 124 so that gyratory plate 106 may pivot around pivotpin 132 while under compressive forces from hydraulic cylinder 20.

In operation, gyratory compactor apparatus 10 is useful for testingsample material S by subjecting sample material S to compaction andsheer forces secondary to compression of sample S with concurrentgyratory tilting of the specimen container. With top 32 in an openretracted position suspended on lid lift 74, sample material S, such asheated asphalt may be placed into the space defined within cylinder wall36. Sample cap plate 44 may then be placed on top of material sample Sand top 32 centered over cylinder housing 12 to which it can then beclamped securely with lid clamps 68. Mold cylinder 14 is kept at theappropriate temperature using mold heater 37. In the instant example,using heated asphalt the temperature is kept at 300 degrees Fahrenheit.

Sample material S is then initially compacted by controlling cylinder uprelay 202 activating cylinder rod drive 200 to bring the pressure, asmonitored through load cell 56, up to the testing parameter. In testingasphalt, the approximately 8 pound sample of asphalt is compacted to apressure of 600 Kpa.

On arriving at this initial compaction pressure, an initial cylinderheight measurement is taken which yields an initial density value, sincesample volume can be determined from sample height and cross-sectionalarea. Additionally, this initial density reading may be used toindirectly arrive at the percentage of air voids by knowing thecomponent densities of the rock and bituminous asphalt used in themixture.

Introduction of shear forces is accomplished through activation of themotor in a clockwise direction which turns cam 80 so as to engageplunger 100 compressing plunger 100 against constant tension springwashers 104, in the preferred embodiment these are a plurality ofBellville washers, pivoting gyratory plate 106 about pivot pin 132 andradially displacing the center of gyratory plate 106 and angular contactbearing 118 off of the longitudinal axis of cylinder housing 12. Thisdisplacement of the center of gyratory plate 106 and angular contactbearing 118 displaces the upper end of cylinder wall 36 with themplacing a tilt in cylinder wall 36. The degree of tilt imposed oncylinder wall 36 is primarily determined by the amount of radialdisplacement gyratory plate undergoes. Greater accuracy andreproducibility is possible in conjunction with an adjustable tiltingstop such as second angular adjustment rim 18. As gyratory platedisplaces radially taking angular contact bearing and cylinder mold 14with it, when rounded second end 40 reaches beveled surface 46, nofurther tilting of cylinder mold 14 may occur. Any additional rotationof gyratory cam 80 displacement is taken up by constant tension springwashers 104 being compressed between plunger 100 and inner bearing race120. Therefore, the firm stop provided by second angle adjustment rim 18ensures an accurate, reproducible tilt angle. Angular tilt of cylinderwall 36 may be checked by determining the degree of displacement ofplungers 162 and 168. By knowing the distance between the plungers, itis then easy to directly calculate the angular tilt. If adjustment isneeded, second angular adjustment rim 18 may be raised or lowered asnecessary through adjustment of gyratory angular adjustment screw 50 toraise or lower adjustment blocks 48. As mentioned above in the presentembodiment three such adjustment blocks 48 with their concomitant heightadjustments are used.

As gyratory cam 80 turns clockwise, as referenced by the motor,eventually gyratory drive surface 88 comes to abut against gyratorydriven surface 96 of cam housing 92. At this point in the rotation ofgyratory cam 80, the relative motion of gyratory plate 90 in relation todriven plate 124 ceases. This transitioning is represented in referenceto FIGS. 6 and 7. In FIG. 6, as viewed from the bottom, gyratory cam 80is in its non-gyratory position with non-gyratory drive surface 84intimately contacting non-gyratory driven surface 98 of cam housing 92.In this position, gyratory plate 90 is concentric about the longitudinalaxis of cylinder housing 12 and driven plate 124 as represented by thecenter of drive shaft sleeve 86. Pivot pin 132, slot pin 134, slot 112and clearance hole 114 are drawn in phantom to better display theirpositional relationship changes between FIGS. 6 and 7. Additionally,that portion of plunger 100 and plunger stem 102 along with Beltvillewashers 104 within cam plate 90 are also drawn in phantom.

In turning drive shaft 64 in a clockwise direction, which is acounterclockwise direction as viewed from below in these two Figures,gyratory cam 80 rotates counterclockwise in these views until gyratorydrive surface 88 comes into intimate contact with gyratory drivensurface 96. During this motion, plunger engaging surface 82 has slidpast plunger 100 until it has reached its maximal degree of lift. Themotion of gyratory cam 80 relative to plunger 100 causes a pivoting ofgyratory plate 90 about pivot pin 132. Secondary to the pivoting ofgyratory plate 90 about pivot pin 132, the entire gyratory plate 90rotates and translates to a new position designated as gyratory plate90'. Pivot pin 132 and slot pin 112 have remained in place because therehas been no motion in driven plate 124 as yet, but as can be seen, pinslot 112 and clearance hole 114 have moved relative to slot pin 134 anddrive shaft sleeve 86, respectively. The relative position of drivenplate 126 is shown in phantom in FIG. 7.

For a preferred embodiment, the degree of gyratory shift in gyratoryplate 90 is 0.25 inches with a total plunger 104 motion of 0.25 inchesplus an additional 0.054 inches in order to put a specified load on tothe plurality of Bellville washers 104. This degree of eccentricity isused to tilt cylinder wall 36 so as to engage around its second end 40against second angle adjustment rim 18. For purposes of clarification inthe present embodiment, gyratory cam 80 has moved through an arc ofapproximately 84 degrees and gyratory plate 90 has rotated approximately17 degrees 30'.

Continued rotation of drive shaft 64 continues to impart rotationalmotion in gyratory cam 80 which is translated through to cam plate 90gyrating cam plate 90 about an axis at an angle to the longitudinal axisof drive shaft 64 which is on the longitudinal axis of cylinder housing12. This continued motion is translated into a gyratory tilting ofcylinder wall 36 against second angle adjustment rim 18. End plates 42and 44 remain perpendicular to the longitudinal axis of cylinder housing12 and parallel to each other thus imparting a shear force throughsample material S as the gyratory tilt moves about and around thelongitudinal axis of cylinder housing 12. Thrust forces exerted upthrough second end plate 44 into cam plate 90 and gyratory plate 106 aretranslated through thrust bearing 150 into driven plate 124. Any offcenter moments of force created by the eccentric placement of gyratoryplate 90 is counteracted through the relationship of drive shaft sleeve86 within drive shaft sleeve hole 130 and dissipated through upperangular contact bearing 136 against top 32.

I claim:
 1. A gyratory compaction apparatus for creating compression andshear forces in a sample material, the apparatus comprising:a hollowcylinder mold open at first and second ends, and including first andsecond end plates in slidable engagement with an inner surface of themold proximate respective first and second open ends defining a chamberwithin the mold between the first and second end plates suitable forreceiving the sample material; a support frame having a hollowcylindrical interior suitable for receiving the mold therein generallyaligned along a support frame longitudinal axis; compression means,mountable on the support frame and operably engaging the first endplate, for compressing the sample material within the chamber betweenthe first and second end plates; and a gyratory tilt assembly, removablymountable to the support frame proximate the mold second open end andoperably engageable with an inner surface of the hollow cylinder mold,comprising:rotational drive means for reversibly rotating the gyratoryassembly; a cam operably attachable to the rotational drive means; agyratory plate having an inner housing for encompassing and operablyengaging the cam, the housing having a cam contact surface, a springbiased plunger operably engaging the cam, and a first angle contactbearing for operably engaging the inner surface of the mold proximatethe second open end; and a driven plate operably engagable between thesupport frame and the gyratory plate, having a second angle contactbearing operably engaging the support frame concentrically around thesupport frame longitudinal axis, and operably coupling to the gyratoryplate with a pin mounted eccentric to the support frame longitudinalaxis and an annular planar thrust bearing concentric to the pin; so thatwhen the rotational drive means rotates the cam in a first direction,the cam engages the cam contact surface and the gyratory plate isrotated concentrically about the support frame longitudinal axis, andwhen the rotational drive means rotates the cam in an opposite seconddirection, the cam engages the plunger pivoting the gyratory plate aboutthe pin so that the gyratory plate rotates and moves radially inrelation to the support frame longitudinal axis rotating eccentricallyto the support frame longitudinal axis moving the first angular contactbearing about the inner surface of the mold proximate the second openend tilting the cylinder mold to an angle relative to the support framelongitudinal axis and gyrating the mold about the support framelongitudinal axis while maintaining the angle.
 2. The apparatus of claim1 in which the support frame includes:a circular rim concentric to thesupport frame longitudinal axis and having an outer beveled surfacesuitable for operably supporting the mold open first end in tiltableengagement; and a circular ring adjustably mountable to an inner surfaceof the support frame concentric to the support frame longitudinal axishaving an inner beveled surface suitable for operably engaging the moldopen second end.
 3. A gyratory compaction apparatus for creatingcompression and shear forces in a sample material, the apparatuscomprising:a support frame having a frame longitudinal axis andincluding a first circular rim with an inner beveled surface and asecond circular rim with an outer beveled surface with the first andsecond circular rims concentric to the frame longitudinal axis; a hollowcylinder mold open at a first end and a second end, mountable within thesupport frame with the second end supportable by, and tiltable on, thesecond rim beveled surface, the first end suitable for operably engagingthe first rim beveled surface, the mold suitable for receiving thesample material therein and having a mold longitudinal axis; compressionmeans, mountable on the support frame below the cylinder mold, suitablefor compressing the sample material within the mold along the framelongitudinal axis; and a gyratory tilt assembly removably mountable tothe support frame proximate the mold first end operably engageable withthe mold proximate the first end; so that when the gyratory tiltassembly operates in a first direction, the mold longitudinal axis isoperably placed in alignment with the frame longitudinal axis, and whenthe gyratory tilt assembly rotates in an opposite direction, thegyratory tilt assembly engages the mold proximate the first end, tiltingthe first end to engage the first rim beveled surface and tilting theaxis of the mold longitudinal axis in relation to the frame longitudinalaxis.
 4. The apparatus of claim 3 in which the gyratory tilt assemblyincludes a roller suitable for rollable engagement of an inner surfaceof the mold.
 5. The apparatus of claim 3 in which the mold includesfirst and second end plates in slidable engagement with an inner surfaceof the mold.
 6. The apparatus of claim 3 in which the compression meansincludes a hydraulic cylinder and rod.
 7. The apparatus of claim 3further comprising control means for controlling the gyratory assemblyand the compression means.
 8. The apparatus of claim 3 in which thegyratory assembly includes:drive means, attachable to the support frame,for reversible rotation of the gyratory assembly; a cam operablyattachable to the drive means; a roller operably engaging the cam; and adriven plate operably mounted between the support frame and the rollerincluding a pivot pin mounted eccentric to the frame longitudinal axisand engageable with a pin hole in the roller.
 9. The apparatus of claim8 in which the roller includes a spring biased plunger mountable withinthe roller suitable for operably engaging the cam.
 10. The apparatus ofclaim 8 in which the roller includes a gyratory plate having an innerhousing for encompassing the cam and an outer bearing suitable forengaging the mold.
 11. The apparatus of claim 8 in which the drive meansincludes a motor having a drive shaft aligned with the framelongitudinal axis suitable for attachment with the cam.
 12. A gyratorycompaction apparatus for creating compression and shear forces in asample material, the apparatus comprising:a hollow cylinder mold, openat both a first end and a second end, suitable for receiving thematerial therein, having an inner surface and a mold longitudinal axis;a support frame, having a frame longitudinal axis, suitable forsupporting the mold in a tiltable engagement relative to the framelongitudinal axis; compression means, mountable on the support framebelow the cylinder mold, suitable for compressing the sample materialwithin the mold along the frame longitudinal axis; and a gyratory tiltassembly removably mountable to the support frame proximate the moldfirst end and having a roller operably engageable circumferentially withthe mold inner surface proximate the first end; so that when thegyratory tilt assembly operates the roller in a first direction, themold central longitudinal axis is in alignment with the frame centrallongitudinal axis, and when the gyratory tilt assembly rotates theroller in an opposite direction, the roller rollably engages the innersurface of the mold proximate the mold first end, tilting the mold firstend and tilting the axis of the mold longitudinal axis relative to theframe longitudinal axis.
 13. The apparatus of claim 12 in which thesupport frame includes a first circular rim with an inner beveledsurface for operably engaging the mold first end and a second circularrim with an outer beveled surface for supporting the mold at the moldsecond end, with the first and second circular rims concentric to theframe longitudinal axis.
 14. The apparatus of claim 12 in which the moldincludes first and second end plates in slidable engagement with aninner surface of the mold.
 15. The apparatus of claim 12 in which thecompression means includes a hydraulic cylinder and rod.
 16. Theapparatus of claim 12 further comprising control means for controllingthe gyratory assembly and the compression means.
 17. The apparatus ofclaim 12 in which the gyratory assembly includes:drive means, attachableto the support frame, for reversible rotation of the gyratory assembly;a cam operably attachable to the drive means and operably engageablewith the roller; and a driven plate operably mounted between the supportframe and the roller including a pivot pin mounted eccentric to theframe longitudinal axis and engageable with a pin hole in the roller.18. The apparatus of claim 17 in which the roller includes a springbiased plunger mountable within the roller suitable for operablyengaging the cam.
 19. The apparatus of claim 17 in which the rollerincludes a gyratory plate having an inner housing for encompassing thecam and an outer bearing suitable for engaging the mold.
 20. Theapparatus of claim 17 in which the drive means includes a motor having adrive shaft aligned with the frame longitudinal axis suitable forattachment with the cam.